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DeviceNet 2400, 2500, 26/2700.

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Presentation on theme: "DeviceNet 2400, 2500, 26/2700."— Presentation transcript:

1 DeviceNet 2400, 2500, 26/2700

2 This Talk DeviceNet - Background DeviceNet v. Profibus DP
Operation of 26/2700 Operation of 2400 and 2500

3 DeviceNet Based on CAN (Controller Area Network)
CAN provides deterministic “peer-to-peer” networking DeviceNet is to CAN as Modbus is to RS485 Higher Level Protocol designed for Industrial applications Power available on the same cabling (up to 8 amps at 24VDC) Designed by Allen Bradley as proprietary fieldbus for linking simple devices (e.g. limit switches) to a central PLC Now fully “open” and owned by ODVA (Open DeviceNet Vendors Association)

4 DeviceNet Usually uses a PLC “Master” and “Slave” devices
Typically very simple networks (< 600 bytes of Input and Output for the whole network). Limited data capacity, imposed by slow maximum speed (500K), and CAN limitations Limited physical network length (discussed later) DeviceNet can support complex peer-to-peer networks and more complex devices. However in practice, this is almost never done.

5 I/O Data Transfer Model
Slave Input Data (To PLC) PLC Registers Temperature Working Setpoint Loop Output Power Alarm Status word Slave Output Data (From PLC) Target Setpoint Manual Output Application uses data from input registers and sets values in output registers Scanner transfers I/O Data from/to PLC once each scan cycle for each slave ~ 10mS cycle

6 I/O Transfer Methods “Polled” I/O Master requests Input values from slave and sends Outputs on each bus cycle “Cyclic” I/O Slave sends data at predefined time intervals Change of State (“COS”) Slave sends data only when a change of value has been detected. Bit Strobe A very efficient way of requesting a small amount of data (less than 4 16 bit words) from a slave device. Most often used method is Polled I/O - others useful to increase throughput

7 DeviceNet “Objects” DeviceNet devices made up of a set of “Objects”
Really just a way of organising parameters by functions Values are addressed over comms by: “Class” - a number defining the type of object from a predefined list (e.g. Class 1 is a “DeviceNet identity” object holding information on Device model and manufacturer.) “Instance” - If more than one object of a given class exists, this number identifies a particular instance. “Attribute” - a number between 0 and 199 defining the parameter within the object. Objects accessed using “explicit messaging”.

8 Explicit Messaging Like Modbus, i.e. a single shot read or write request. Read or write an object by class/instance/attribute. Typically used by Configuration Tool to configure or commission a slave device Can also be used by a PLC master to access infrequently used variables in a slave Used in 2600 and 2700 to write program data

9 “EDS” files and Commissioning
A bit like Profibus GSD files - define device capabilities However No “GSD file editor” equivalent in DeviceNet - Eurotherm slaves configured using standard DeviceNet tools.

10 DeviceNet v. Profibus DeviceNet Profibus DP Max Speed 12 Mbaud
Max speed 500 kbaud 125 kbaud 250 kbaud 500 kbaud Max Nodes 64 per network Power supplied by network Complex and extendable architecture Flexible trunk/drop topology Self Declaration of Nodes Profibus DP Max Speed 12 Mbaud 500 kbaud 1.5 mbaud 12 mbaud Max Nodes 32 per segment, 128 per network (with repeaters. No Power on network Simple, fixed architecture Trunk only topology Fixed network configuration Profibus DP is generally simpler to use and more capable. The only real practical advantage to DeviceNet is when linking into Allen Bradley/Omron systems

11 2600/2700 on DeviceNet Fully Configurable I/O Messaging 0 to 60 “Input” variables (from PLC) 0 to 60 “Outputs” (sent to PLC) Polled/Cyclic/COS/Bit Strobe available Configured via an ‘Assembly Configuration Object” using standard Rockwell tools Support for 32 bit (IEEE floats and long integers) “Application” Object Allows explicit messaging access to 200 frequently used variables Includes 32 configurable ‘attributes’ assignable to any instrument parameter “Tag Access” object Permits Modbus style ‘block’ read and writes. Used for program download and access to infrequently used variables. Currently under Beta test for release around April

12 2400 on DeviceNet Same as 26/2700, except:
Only 10 configurable parameters in “Application Object” No support for IEEE numbers Available for beta test: release scheduled for May/June.

13 2500 on DeviceNet As 2600/2700 except ALL 200 parameters in the application object are configurable Beta test units available: release scheduled for April/May

14 Some closing remarks With the release of the new DeviceNet interface, Eurotherm will have a very complete and scalable DeviceNet offering, from 2200 up through 2700. Should be possible to repeat success of Profibus with DeviceNet Consider targeting Allen Bradley and Omron OEMs Consider what further training you would like!

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